1. Field of the Invention
The present invention relates to a multiple resolution scanning device, particularly to a multiple resolution scanning device, which allows to shift resolutions without using mechanical means.
2. Description of Related Art
A scanning device used in a conventional scanner provides scanning of a scanned object at a single resolution only. Scanning at various resolutions requires using different scanners to accommodate needs for various resolutions. For example, scanners for the popular A4 format and for negative films have been brought on the market.
Multiple resolution scanners have appeared on the market to meet the demand for various resolutions in a single device. A conventional multiple resolution scanner usually has a lens group of lenses of different resolutions, a mirror group, a detector (charge coupled device), and a driving device to shift the lenses of the lens group. The driving device moves the lens group, bringing one of the lenses of the lens group on front of the detector for scanning at a specific resolution. Although conventional multiple resolution scanners allow scanning at various resolutions, space is needed for accommodating the moving lens group and the driving device, requiring a large volume of the scanner. Furthermore, since the lenses are movable, positions thereof are not stable, impairing quality of scanned images.
In U.S. patent application Ser. No. 09/087,328 a multiple resolution scanning device has been disclosed, having a plurality of lenses of various resolutions, a plurality of detectors, one detector for each lens, and a mirror group, consisting of a plurality of mirrors. The lenses are mounted in fixed positions, each on front of one detector. A multiplexer transmits signals from one of the detectors to a signal processing unit. Thus scanned objects are read by scanning at one of several resolutions.
Since the lens group of this multiple resolution scanning device is not moved, no driving device is needed, reducing the volume of the scanning device. The lenses are fixed relative to the detectors, ensuring high image quality. However, the multiple resolution scanning device uses various light paths for the various resolutions, each passing through one of the lenses. To avoid interference between the various light paths, the lenses have to be placed apart from each other in an appropriate arrangement.
Furthermore, at various resolutions, the scanned objects are scanned at equal scanned areas. Then the light paths through all the lenses partially overlap using common areas of the mirrors, and the lenses need to be adapted accordingly to the mirrors. This leads to a complicated arrangement of the lenses and the mirrors, resulting in a greater number of mirrors and an increased volume.
It is the main object of the present invention to provide a multiple resolution scanning device with a simplified mirror group, requiring less volume.
Another object of the present invention is to provide a multiple resolution scanning device of simple design and structure.
The present invention can be more fully understood by reference to the following description and accompanying drawings.